Switch for oil well pumping equipment



Oct. 29, 1935. o, A, AvlNs 2,018,946.

SWITCH FOR OIL WELL PUMPING E QUIPMENT Filed Sept. 24, 1952 I9 I27 29) I5) 30 a 13 2a 94 26 16 /a 17 2/ '25 lnveniar Patented Oct. 29, 1935 UNITED STATES PATENT OFFICE SWITCH FOR OIL WELL PUMPING EQUIPMENT Application September 24, 1932, Serial No. 634,733

2 Claims.

This invention relates to switches for well pumping equipment and particularly to one which may be adapted to stop the prime mover in case of accident or breakage of the moving parts of the pump.

In the pumping of deep wells, particularly oil wells, gas engines are widely employed as they are readily supplied with fuel from the gas produced with the oil. In some cases, where electric power lines are available, electric motors may be used for pumping. The mechanism for transforming continuous rotary motion to slow speed reciprocating motion may be the same in eithercase. The differences will be pointed out in the following description.

In gas engine driven installations the engine is usually fitted with a pulley and is belted to another larger pulley or band wheel, which latter is fitted with a crank and wrist pin. This is connected by a pitman to a walking beam, which in turn is connected by a bridle to a clamp or clip on the polished rod of the string of sucker rods, which lead down the well to the reciprocating deep well pump. Counterweights may be fitted -to the walking beam, crank or band wheel in order to balance the weight of the sucker rods and thereby equalize the torque required to operate the pump.

In motor driven installations the pulleys and band wheel may be dispensed with and replaced by a reducing gear and crank driven directly from the motor.

The sucker rods, which connect the walking beam linkage with the pump piston or other mechanism at the bottom of the well, may be several thousand feet in length. They are periodically subjected to extreme tension, impact, wear from rubbing against the tubing, and fatigue producing vibration, as well as to corrosive action from the oil, water and gas in the well. In consequence they are subject to frequent and unannounced failure. In fields where pumping must be used to obtain the oil, the wells may be widely spaced and often one pumper is responsible for wells scattered over several miles of territory. Consequently it has been found to be advantageous and oftentimes necessary that some form of safety device beprovided that will shut down the prime mover in case of rod or pump breakage.

Should a rod part or a wrist pin break, the engine may and often does race or run away, damaging itself and the power transmission equipment from the strains set up by the unbalanced load. This is accentuated in case the well is deep and thesucker rods are long and heavy and where the power transmitting mechanism is fitted with heavy counterweights, which cause a high degree of unbalance in case of rod breakage.

It is an object of this invention to provide a safety device which will shut down a well pumping engine or electric motor in case of failure of the pump rod or other pump mechanism.

Another object is to provide a. safety switch which is safe to use in an atmosphere which may contain an inflammable mixture of gas and air.

Another object is to provide a safety switch which is economical to make and use and which may be reset and used repeatedly.

A further object is to provide an enclosed safety switch in which all contacts are protected from corrosion or damage from any source and which is not subject to damage or interference from freezing or from high climatic temperatures.

These and other objects will be more fully apparent from the description which follows, and from the accompanying drawing, which forms a part of this specification and illustrates one application of a preferred embodiment of this invention.

In the drawing:

Figure l is a diagrammatic side elevation of a typical gas engine well pumping installation showing the invention in plane on the walking beam.

Figure 2 is a detail elevation of one form of safety switch constructed according to this invention.

Referring to Figure 1, thenumeral ll represents an oil well derrick of conventional form. on one side of the derrick is the usual housing l2 for a gas driven pumping engine l3. Engine I3 is provided with a pulley I4 and belt I 5, which latter also passes around and drives the band wheel It. The shaft of band wheel I6 is fitted with a crank I1 on which is mounted wrist pin l8, which latter receives the lower end of pitman IS. The upper end of pitman I9 is attached to the outer end of walking beam 20', which is journalled at its midpoint on the top of Samson post 2 I. v

The derrick end of walking beam 20 is provided with a hanger 22 for the bridle of the polished. rod clip 23, which in turn supports the polished rod 24. Polished rod 24 passes through the usual stufling box on the casing head 25 of the 59 well. Inside the well and not illustrated in the drawing is the usual sucker rod string, which may be a series of steel rods screwed together to give a string of the required length. At the lower end of the sucker rod string is the pump mechanism 55 (not shown) which is reciprocated by means of the foregoing equipment to pump oil from the well.

The usual practice, in order to equalize the torque on the pumping engineor motor, is to counterbalance all or part of the weight of the sucker rod string. This may be done by attaching suitable weights to the outer end of walking beam 20, to the crank l1, or to the band wheel l6 as indicated in this case at 26. A combination of these methods may also be used. Under any circumstances, whether or not a counterweight is used, when the sucker rod string breaks or there is any failure of the pump mechanism, the greatly reduced and considerably unbalanced load often allows the gas engine I3, which may not be provided with an overspeed governor, to run away, causing considerable damage to itself and to its housing, and in some cases to the entire derrick structure. In the case of an electric motor, the consequences of such a breakage are not so serious, but a safety switch of this type has been found to be desirable.

The safety switch may be mounted upon the walking beam 20 as indicated generally at 21 so that greater than normal motion or jarring of the beam caused by a sucker rod failure, for example, would cause the switch to function by short circuiting the magneto or other ignition device 28 on gas engine l3. In the case of a. motor driven pump (not shown), the switch could be used to open or close a suitable circuit in the motor controlequipment, thereby shutting down the motor. The means for doing this are well known and would necessarily vary with each type of control system. Consequently no attempt will be made to describe the exact connections for this application.

Suitable insulated duplex wire, generally designated 29, may be used to connect one of the electrodes 33 of the switch 21 to the low tension terminal of the magneto 28 and the other electrode to a. suitable ground, such as the engine base. The wire may be carried along the walking beam 20 to the Samson post 2|, where it is left in a. loop to allow for the motion between beam 20 and post 2|. The wire may then lead along the belt housing 30 to the engine house I2 and thence to the engine itself or to whatever control equipment is used. It is usually desirable to place an approved type of switch in the wiring system as indicated at 3|, in order that the engine l3 may be run when the pitman I9 is disconnected for pulling tubing or similar operations. This switch 3| should preferably be adapted to be locked so that the safety switch will not be inadvertently or intentionally left out of action.

One form of safety switch 21 which has been found to be satisfactory is detailed in Figure 2 and will now be described. It consists essentially of an open ended glass tube 32, bent substantially as shown, in which two electrodes or contacts 33 have been sealed and which is partially filled with mercury 34. The switch is preferably mounted upon an insulating base 35, which may be of wood and which is attached to the beam 20 (Figure 1) by means of a single bolt 36 and wingnut 31, so that its angular position with regard to the beam 20 and also with the vertical, may be adjusted and fixed. Various modifications in this mounting may be made so long as the angular fixed position of the tube may be controlled.

The electrodes 33 may be of fine copper, nickel alloy or other metal wire suitable for sealing into the end of the glass tube 32. The recurved shape of the lower end of tube 32 may be varied within wide limits, but that shape shown has been found to be satisfactory. The tube 32 is preferably supv ported and guarded against accidental breakage by wooden guard straps 38 and metal clips 39. Its open end may be protected by a metal cap or cover 40 to prevent the entrance of dirt or moisture, which latter might freeze in cold weather and interfere with the proper operation of the switch. 1

A set of dimensions which were found to be satisfactory are as follows: Tube 32 was of M; inch inside diameter glass tubing and was originally approximately 9 inches long. The straight upright portion, tangent to the U bend, was ap- 1 proximately 5 inches long. The vertical distance from the bottom of the U bend to the top of the recurved portion or hump was approximately 1 inch. The end of the recurved portion where the electrodes enter was approximately 5 ,4 inch vertically above the bottom of the U bend.

In the example shown, the switch 21 is attached to the side of the walking beam 23 near its outer end. With the pumping unit shut a down, mercury 34 is poured into the open end of tube 32, whereupon it will flow into the U bend and trap the air in the space above the recurved portion and adjacent the electrodes 33, as indicated in Figure 2. Suiiicient mercury is 3 poured in to give a differential of one or two inches head in the vertical part of the tube above that in the U shaped portion. The switch 21 must then be adjusted by alternately starting and stopping the pumping engine I 3, with the 3 switch 3| in the open position. By loosening the wingnut 31, base 35 maybe rotated slightly around bolt 36 until mercury 34 almost, but not quite, runs from the U shaped section of the tube over the top or hump" of the recurved portion of the tube and down against electrodes 33 when the pump is in operation. In the interest of safety all of the adjustments should be made with the engine shut down. When a satisfactory adjustment is obtained, the wingnut 31 may 4 be clamped and the switch 3| closed, whereupon the safety switch 21 will be ready for action.

In making the adjustment of the switch 21 as outlined above, some allowance should be made for the effect of temperature changes upon the 5 setting. The trapped air in the end of the tube will act somewhat as a gas thermometer and a reduction in atmospheric temperature will cause this air to contract somewhat, thereby tending to draw mercury over into the recurved portion. 5; This will have the effect of making the switch operate at a lower degree of vibration or movement at low air temperatures. This has been found to be of minor importance, however.

In operation, the beam 20 may make from n twenty to thirty strokes per minute, although in some cases a much slower speed may be used. With the safety switch 21 in place on the beam' 20, if any breakage should occur and the engine speed become increased thereby, or should any 5 part become loosened or worn or broken so as to cause more than normal jarring or pounding of the beam 20, the mercury 34 will separate or spatter into small droplets which will splash over the recurved portion of the tube 32. This 7 mercury will accumulate in the well or pocket adjacent the electrodes 33, which will be short circuited, thereby shutting down the engine l3.

To reset the switch 21 after mercury has been jarred into contact with the electrodes 33, it is 7;

only n to loosen the wingnut 31 on bolt 30, and rotate the base 35 clockwise, so that the straight section of tube 32 is almost, but not quite, horizontal, tapping the base at the same time with a stick of wood. The mercury 34 will run back over the recurved portion of the tube 32 and the sealed end of the tube will again become filled with air. Care should be taken not to rotate the base so far that the mercury will run out of the open end of tube 32. The base 35 may then be turned back in a counterclockwise direction to its set or adjusted position, whereupon the switch will be ready for service.

It is obvious that other arrangements of this invention could be made, such as by reversing the electrical functions of the electrodes so as to open an electric circuit upon actuation of the inertia element (mercury) instead of closing it as shown in the drawing. This would call for a small pool of mercury in the tube 32 in the well formed by the downwardly curving end into which the electrodes 33 are sealed. This mercury would be jarred over into the U trap of the tube 32, thus leaving the electrodes electrically separated, when more than normal vibration occurred. Further changes could also be made such as having left hand" and right hand types of switch adapted to be placed on either side or either end of the walking beam 2|].

A safety switch in which mercury was dispensed with entirely could be made without departing from the generic feature of this invention. This could consist of a pair of contacts and an inertia element, which latter could be a weight such as a pendulum free to move, supported by or connected to a moving element of the pumping equipment. The normal motion of the inertia element could be so tuned or adiusted that the contacts remained undisturbed so long as the normal motion cycle or vibration of the pumping equipment persisted, but any change in the latter, particularly an increase in frequency of motion or amplitude of vibration, would cause the inertia element to change the electrical relationship of the contacts, through the interposition of a switch lever or the like, thus acting to shut down the prime mover.

The basic idea of the invention is in the utilization of an inertia actuated means attached to some moving part of the pumping equipment and arranged to make or break a contact when the motion or vibration or cyclic angular position of the moving part is changed and particularly increased, due to breakage of the sucker rods or other load producing or transmitting parts.

Although a specific construction embodying this invention has been described and illustrated, it is to be understood that the invention is not limited to that specific device and such modifications and changes as come within the scope of the appended claims are embraced thereby.

I claim:

1. A safety switch for well pumping apparatus comprising a base adapted to be secured to a 25 normally moving part of the apparatus, an insulating receptacle fixed to said base, said receptacle being separated into two portions by an intervening upwardly extending barrier, a pair of electrodes extending into one of said portions and a mobile metallic body in the other of said portions, said mobile body being responsive to excessive speed of vertical motion of said apparatus to pass over said barrier and contact said electrodes, said body constituting the only moving part of said switch.

2. A safety switch for well pumping apparatus according to claim 1 in which said mobile metallic body comprises a quantity of mercury.

OMAR A. cAvINs'. 

